The present invention relates to Pb-free soldering alloy which does not include Pb.
Eutectic soldering alloy which comprises Sn in 60 wt. % and Pb in 40 wt. % or which comprises Sn in 63 wt. % and Pb in 37 wt. % has been used for a long time in the field of the jointing technology of electronic parts.
In case an electronic device assembled by soldering by use of Pb-rich solder is put on a waste yard, there arises an environmental problem that acid rain dissolves Pb out of the solder joint and contaminates the underground water. It is said that when Pb enters a human body Pb puts the central nerve out of order and causes a hemoglobin trouble in the blood.
Thus it is the purpose of the present invention to propose Pb-free soldering alloy which does not include any amount of Pb to prevent the environment from being contaminated by Pb in case the soldered product is put on a waste yard and which makes it possible to enhance the mechanical strength of the soldered joint by using said Pb-free soldering alloy.
The Pb-free soldering alloy according to the present invention is characterized in that it comprises Cu in 0.05 to 2.0 wt. %, Ni in 0.001 to 2.0 wt. % and Sn in the balance.
According to the present invention, the addition of Ni in 0.001 to 2.0 wt. % to Pb-free Snxe2x80x94Cu soldering alloy enhances the mechanical strength by about 15 to 30%.
Cuxe2x80x94Ni alloy is perfect solid solution and the added Ni is combined with Cu crystallized out of two-elemental Snxe2x80x94Cu alloy as a solid solution. In the result, the mechanical strength of the soldering alloy is enhanced.
Furthermore, as the soldering alloy does not include Pb, even when the soldered product is put on a waste yard, the environment can be prevented from being contaminated.